page_title: Pseudotsuga menziesii var. glauca
section_title: Characteristics
hierarchical_section_title: Pseudotsuga menziesii var. glauca / Characteristics
caption_attribution_description: English: Pseudotsuga menziesii (Douglas fir) foliage along Wheeler Peak Scenic Drive in Great Basin National Park, Nevada
context_page_description: Pseudotsuga menziesii var. glauca, or Rocky Mountain Douglas-fir, is an evergreen conifer native to the interior mountainous regions of western North America, from central British Columbia and southwest Alberta in Canada southward through the United States to the far north of Mexico. The range is continuous in the northern Rocky Mountains south to eastern Washington, eastern Oregon, Idaho, western and south-central Montana and western Wyoming, but becomes discontinuous further south, confined to "sky islands" on the higher mountains in Utah, Colorado, Arizona and New Mexico, with only very isolated small populations in eastern Nevada, westernmost Texas, and northern Mexico. It occurs from 600 m altitude in the north of the range, up to 3,000 m, rarely 3,200 m, in the south. Further west towards the Pacific coast, it is replaced by the related coast Douglas-fir, and to the south, it is replaced by Mexican Douglas-fir in high mountains as far south as Oaxaca. Some botanists have grouped Mexican Douglas-fir with P. menziesii var. glauca, but genetic and morphological evidence suggest that Mexican populations should be considered a different variety.
context_section_description: Rocky Mountain Douglas-fir is a large tree, typically reaching 35–45 m (115–148 ft) in height and 1 m (3 ft 3 in) in diameter, with exceptional specimens known to 67 m (220 ft) tall, and 2 m (6 ft 7 in) in diameter. It commonly lives more than 500 years and occasionally more than 1,200 years. The bark on young trees is thin, smooth, gray, and covered with resin blisters. On mature trees, it is moderately thick (3–6 cm, 1 ¹⁄₄–2 ¹⁄₄ in), furrowed and corky though much less so than coast Douglas-fir.
  The shoots are brown to gray-brown, smooth, though not as smooth as fir shoots, and finely pubescent with scattered short hairs. The buds are a distinctive narrow conic shape, 3–6 mm (¹⁄₈–¹⁄₄ in) long, with red-brown bud scales. The leaves are spirally arranged but slightly twisted at the base to be upswept above the shoot, needle-like, 2–3 cm (³⁄₄–1 ¹⁄₄ in) long, gray-green to blue-green above with a single broad stomatal patch, and with two whitish stomatal bands below.
  The male (pollen) cones are 2–3 cm (³⁄₄–1 ¹⁄₄ in) long, and are typically restricted to, or more abundant on, lower branches. Pollen cones develop over 1 year and wind-dispersed pollen is released for several weeks in the spring.
  The mature female seed cones are pendent, 4–7 cm (1 ¹⁄₂–2 ³⁄₄ in) long, 2 cm (³⁄₄ in) broad when closed, opening to 3–4 cm (1 ¹⁄₄–1 ¹⁄₂ in) broad. They are produced in spring, purple (sometimes green) at first, maturing orange-brown in the autumn 5–7 months later. The seeds are 5–6 mm (³⁄₁₆–¹⁄₄ in) long and 3–4 mm (¹⁄₈–³⁄₁₆ in) broad, with a 12–15 mm (¹⁄₂–⁹⁄₁₆ in) wing. Both coast Douglas-fir and Rocky Mountain Douglas-fir produce abundant crops of seed approximately every 2–11 years. Seed is produced annually except for about 1 year in any 4-to-5-year period.
caption: Foliage
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